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Monday, October 27, 2014

Furbabies vs human babies: what do functional MRIs say?

Do photos of human babies trigger similar responses in our brains to photos of companion animals? (NB I borrowed this human baby for the photo!)

The expression “furbaby” has
crept into the common parlance, and I must confess to using it in a sentence or
two as shorthand to describing the human-animal bond, at least as it is
manifested in certain contexts (my own included).

The practice of adopting and
caring for other species, like dogs and cats, is a common human behaviour
across cultures and places. It has been referred to as “alloparenting”.
Alloparenting occurs when individuals other than the biological parents of
someone play a parenting role toward that someone. For example, if your
grandparents raised you, they were alloparenting. Pet owners are not a homogenous
group and the human-animal bond is far from homogenous, so the term “alloparenting”
doesn’t apply to every human-companion animal situation.

But, aside from that, companion animals bother some
scientists. What possible evolutionary benefit, they ask, is there in looking
after someone else’s baby? Why invest
time and energy in providing for another being? Many studies looking at the
potential benefits of pet ownership are prefaced by such a concern. What’s in
it for us?

Bring on the fMRI, I can feel most of my brain light up at the site of Phil.

One hypothesis that has gathered
much traction is that “happy hormones” such as oxytoxin, beta-endorphin,
prolactin, beta-phenylthylamine and dopamine are increased in positive
interactions with pets. They’re also “bonding” hormones in people.

So are we bonding to pets the way
we bond to babies?

A team of researchers from
Massachusetts General Hospital and Harvard Medical School got together to work
out if the attachment looks the same on the brain level (see the full paper here).

They compared interviews and
functional magnetic resonance imaging (fMRI) patterns in mothers viewing
photographs of their own child and their own pet dog, as well as an unfamiliar
child and unfamiliar dog.

The mothers were 22-45 years old,
had at least one child who was 2-10 years old, had at least one dog for at
least two years, and were generally healthy. A complete data set was collected
from 14 participants – so we’re talking a reasonably small number here.

In interviews, mothers reported
images of their own child and dog as eliciting similar levels of excitement/arousal
and pleasantness (valence), although they were bigger differences in the
response to own vs unfamiliar child than there were to own vs unfamiliar dog.

The pleasantness a mother felt
when seeing her own dog’s photo was positively correlated to how attached she
was to her own dog, which makes sense.

Viewing photographs of their own
child was associated with activity in the midbrain (specifically the ventral tegmental
area/substantia nigra, an area rich in dopamine, oxytocin and vasopressin).
This area of the brain is thought to be critical in reward/affiliation – but it
was NOT activated by images of the dog.

Viewing photographs of their own
dog was associated with a more posterior cortical brain activation pattern
involving fusiform gyrus (usually responsible for visual processing, social
cognition). The authors speculate that maybe we find dogs harder to read so there is a lot more processing of visual cues.

The amygdala, believed to be an
important region for bonding, was activated by both familiar child and familiar
dog images.

So the researchers conclude that
mother-child and mother-dog bonds are same-same but different: they share
aspects of emotional experience and patterns of brain function (at least as
apparent on fMRI), but there are also differences in the brain’s activity which
might reflect differences in these relationships. It doesn't quite solve the mystery of "alloparenting" but provides another piece of information in the puzzle.

On a related note, if you’ve ever
contemplated introducing a human baby where you have a pre-existing furbaby,
check out this post.

Veterinary Ethics: Navigating Tough Cases

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